This invention deals with the field of machine tools of the type that includes two independent carrying tool broaches and especially to adaptations allowing to perform with such machine tools a machining in the best conditions of rapidity and precision.
In order to improve the productivity of machine tools such as very high speed machining centres, the designers of machine tools have developed in the course of the last years machine tools called bi-broach machine tools implementing two independent carrying tool broaches instead of a single broach.
It was noticed that on mono-broach machining machine tools at very high speed, the effective cutting time only represented half of the time of use of the machine tool, the remaining of the time being used for the changing of tools. As a matter of fact, by improving the running time as well as the rapidity of the machinings, and by providing the machine tool with a great quantity of tools in order to allow it to offer a great range of machining possibilities, the designers noticed that the time for the changing of tools represented the main difficulty to solve for the optimization of the productivity of a machine tool. A first solution to such problem having been to decrease the machining time, another solution was to develop a machine tool concept, which adopted not a single carrying electrobroach slide mobile along three axis but two carrying electorobroach slide mobile along three axis. A great advantage of such concept is to allow the machining of a piece with a first carrying tool broach while the second broach is changing tools, and vice versa. Therefore, when a machining phase is performed by a rotating tool placed at the extremity of a first carrying electrobroach slide is achieved on the piece, a second phase may start without any resting time by means of a rotating tool placed on the extremity of the second carrying electrobroach slide, the first slide moving away from the piece and moving towards its device of tool changing.
It was noticed that the gain of productivity obtained greatly compensated the overcoat due to the purchase of a machine tool of the bi-broach type when compared to a machine tool of the mono-broach type.
However, classical machine tools, which adopt the bi-broach concept, experience a decrease of productivity and efficiency because of the use of a motorisation of the ballscrew type, the performances of which do not always meet the criteria of performance rapidity and of reliability of the very high speed machining.
In order to optimize the productivity of such machine tools implementing two carrying tool slides, especially in the drive in motion of said slide, the applicant led researches that led to a machine tool of a bi-broach type ensuring machinings more rapidly by implementing a motorisation and a kinematic architecture adapted to said motorisation, particularly new and inventive.
According to the main feature of the invention, the machining machine tool of the type that ensures the putting in motion along at least three axis of two carrying electrobroach slides, it remarkable in that said motions are implemented by means of linear motors.
Such feature is particularly advantageous in that a kinematic structure using the bi-broach concept is provided with a motorisation ensuring a great speed in the motions of the various modules of said architecture and along the three axis. Therefore, not only the changing of tools may be done in hidden time, that is a broach may change tools while another one performs a machining, but also the running times of such slide will be decreased by means of linear motors. Indeed, linear motors that are better suited for high speed machining, especially when they function in pairs, have for advantage to provide great accelerations and an optimal precision in their displacement.
Moreover, the association of a new motorisation with a kinematic architecture using the bi-broach concept led the applicant to imagine a kinematic structure adapted to such association.
Thus, according to a particularly advantageous feature of the invention, when the machine tool is of the type that is provided with a plurality of guiding means corresponding to linear motions along three axis X, Y and Z of the two slides, each one of them being associated to a linear motorisation provided by one or several linear motors of the type where each one of them contains a mobile primary block and a fixed secondary block, said machine tool is remarkable in that the independent and mobile primary blocks of said linear motors ensuring the independent rectilinear motion of each of the two slides along at least one of the three axis, share two by two a single and same secondary block.
Therefore, the applicant is advantageously making full use of the components of a linear motorisation in order to decrease the number of pieces on a same axis of motion, a single secondary block for two primary blocks that are each linked to a different mobile part.
Likewise, according to another particularly advantageous feature, said linear motors, the primary blocks of which share two by two a single and same secondary block, share two by two a single and same measuring rule on which there is a motion of as many cursors as they are primary blocks. The fundamental concepts of the invention having been set forth in their most elementary form, other details and features will come forth more clearly when reading the following description with respect to the attached drawings, giving a non limiting example an embodiment of a machine tool according to the invention.